The invention is used for example in the field of automation technology for controlling continuous processes, in particular in the chemical, process engineering or pharmaceutical industry. To increase unit availability, a second redundant module is hereby connected in parallel to an output module provided for example to output an electrical signal to activate an actuator. If the one module fails, the output signal can still be supplied by the second module.
The parallel connection of redundant digital output modules to increase unit availability is known from the manual “SIMATIC—Automatisierungssystem S7-400H—Hochverfügbare System” (SIMATIC—Automation system S7-400H—High availability system), 01/2004 edition. A digital output signal is supplied here by two modules connected in parallel on the output side, such that the signal is still available even if one module fails. A diode is integrated in the parallel connected modules for each channel, preventing the modules influencing each other (see FIG. 1). Modules with a diagnosis function for identifying a wire breakage are also known from this manual.